1. Field of the invention
The present invention relates to a traveling system for construction equipment, which can secure an initial traveling manipulability regardless of a low-speed traveling (i.e. a first-speed traveling in which an inclination angle of a swash plate of a hydraulic motor becomes maximum) or a high-speed traveling (i.e. a second-speed traveling in which an inclination angle of a swash plate of a hydraulic motor becomes minimum) in accordance with an operator's manipulation of a traveling speed selection switch.
More particularly, the present invention relates to a traveling system for construction equipment, which can improve an initial fine manipulability by compensating for a part where a driving pressure is increased through relative increase of hydraulic fluid being supplied to a driving motor in comparison to a low-speed traveling of a traveling device when a high-speed traveling of the traveling device is selected.
2. Description of the Prior Art
As illustrated in FIGS. 1 and 2, according to a conventional traveling system for construction equipment, a traveling spool for controlling hydraulic fluid being supplied to a traveling motor has the same open area regardless of a low-speed traveling or a high-speed traveling of the construction equipment. Also, the discharge flow rate of a hydraulic pump that supplies the hydraulic fluid to the traveling motor is in proportion to the manipulation amount of a manipulation lever regardless of the traveling speed of the construction equipment.
In this case, a curve “a” indicates an open area for each stroke of the traveling spool for controlling the flow rate of hydraulic fluid being supplied from the hydraulic pump to the traveling motor, and “b” indicates an open area for each stroke of the traveling spool for controlling the flow rate of the hydraulic fluid returning from the hydraulic pump to the hydraulic tank.
On the other hand, in the case of the low-speed traveling of the construction equipment, relatively high torque is generated in comparison to the high-speed traveling. That is, in the case of the low-speed traveling, relatively low driving pressure is generated in comparison to the high-speed traveling, and thus the load pressure is increased at the second traveling speed rather than at the first traveling speed.
Accordingly, in order to move the construction equipment, it is required to further increase the manipulation amount of the manipulation lever in the case of the second-speed traveling, and in this case, it is required to further increase the supply flow rate of hydraulic fluid being supplied to the traveling motor in comparison to the case of the first-speed traveling. In this case, since the start of the construction equipment is made contrary to the intention of an operator who manipulates the manipulation lever, the initial manipulability is lowered.
Due to this, if the open area of the traveling spool is designed to match the low-speed traveling of the construction equipment, pilot signal pressure is heightened at an initial state where the construction equipment starts its traveling in the case of the high-speed traveling of the construction equipment.
By contrast, if the open area of the traveling spool is designed to match the high-speed traveling of the construction equipment, the initial fine manipulation becomes sensitive in the case of the low-speed traveling of the construction equipment.